Electron multiplier gate



July 27, 1965 J. NORMAN ETAL 3,197,653

ELECTRON MULTIPLIER GATE Filed June 4, 1962 2 Sheets-Sheet 1 INPUTINVENTOR. JAMES NORMAN HAYDEN SMITH BY ROBERT THOMPSON AT RNEY y 27,1955 J. NORMAN ETAL 3, 97,663

ELECTRON MULTIPLIER GATE Filed June 4, 1962 2 Sheets-Sheet PULSE SOURCE+2|oo v 30 -2ooo v OSC|LLO INPUT SCOPE INVENTOR. JAMES NORMAN HAYDENSMITH BY ROBERT R.THOMPSON United States Patent 3,197,663 ELECTRONMULTIPLIER GATE Harries Norman, Blacksburg, Va., and Hayden Smith, In,Whitmore Lake, and Robert R. Thompson, Livonia, Mich, assignors to TheBendix Corporation, Southfield, Mich, a corporation of Delaware FiledJune 4, 1962, Ser. No. 199,798 4 Claims. (Cl. 313103) This inventionrelates to a gate for an electron multiplier and more particularly to agate for a channel electron multiplier.

In copending patent application U.S. Serial No. 23,574, filed April 20,1960, by George W. Goodrich and W. C. Wiley, now Patent No. 3,128,408,there is fully'disclosed a tube type channel electron multiplier. Inthis type multiplier, the inside surface of the tube is conductive andhas secondary emissive properties. Upon the application of a voltagedifference between the ends of the tube, current flows through the tubeand produces an electric field in an axial direction through the regiondefined by the tube. Electrons entering the input end of the tube aremultiplied through secondary emission before they emerge from the outputend of the tube. 1 a

This invention relates to gating apparatus for channel electronmultipliers. In accordance with the invention, a first channel electronmultiplier which is to be gated has positioned at its output second andthird channel electron multipliers which comprise the gating apparatus.The electrons emerging from the first channel are gated into the secondor third channel, depending upon the voltage applied to the inputs ofthese channels.

An object of this invention is to provide gating apparatus for theoutput of an electron multiplier.

Another object'is to provide gating apparatus comprising a pair ofchannel electron multipliers positioned at the output of an electronmultiplier to gate the output through one channel or the other uponapplication of a suitable voltage to the input of the appropriatechannel.

Other objects and advantages will become apparent from the followingdetailed description and from the appended drawings and claims.

In the drawings:

FIGURE 1 is a perspective view, partly broken away, illustrating anembodiment of this invention.

'FIGURE 2 is a schematic diagram partly in block form and partly incross section, illustrating the embodiment in FIGURE 1 and showing theassociated electrical circuitry.

FIGURE 3 is another schematic diagram similar to FIGURE 2 which showsthe path followed by electrons when certain electrical conditions exist.

In FIGURE 1, a channel electron multiplier is posi tioned to receiveparticles, such as ions or electrons, from a source (not shown). Forexample, the channel 10 may receive ions from a time-offlight massspectrometer of the type disclosed in US. Patent No. 2,685,035, issuedto William C. Wiley and these ions would produce secondary emission ofelectrons upon striking the inside surface of the channel 10. Positionedat the output of the channel 10 is gating apparatus generally indicatedat 11 which includes a pair of channel electron multipliers 12 and 14.The channels 12 and 14 are positioned to receive electrons emerging fromthe channel 10 and form a Y arrangement with the channel 10. Anodes 16and 18 are disposed respectively at the output ends of the channels 12and 14 to collect electrons passing through the channels. An insulator20 provides insulation between the channels 12 and 14.

Direct voltages of suitable magnitude are applied to the elementsdisclosed above from a direct voltage source 3,197,663 Patented July 27,1965 ice (not shown). For example, as shown in FIGURE 2, direct voltagesof 2,000 volts, 0 volts, '100 volts, +2,000 volts, and +2,100 volts maybe applied respectively, to the input of the channel 10, the output ofthe channel 10, the inputs of the channels 12 and 14, the outputs ofthe. channels 12 and 14 and the anodes 16 and 13. The inputs of thechannels 12 and 14 at l00 volts, are normally maintained at a negativepotential with respect to the output of the channel 10 at 0 volts.

A pulse source 22 is connected to the inputs of the channels 12 and 14through resistances 24 and 26 respectively. The pulse source 22 isadapted to provide an input pulse, such as +200 volts, to either thechannel 12 or the channel 14 to raise the input of the channel to apositive potential volt-s) with respect to the output of the channel 10during application of the pulse. A detector, such as an oscilloscope 28,is connected to the anodes 16 and 18 through resistances 30 and 32,respectively, to detect the electrons striking the anodes.

It should be understood that the channels 10, 12 and 14, and the anodes16 and 18 operate in' a vacuum tube at a pressure of approximately 10*mm. Hg.

When electrons are introduced to the input end of the multiplier 10,they successively strike the surface of the channel 10 as shown by thepath 40 in FIGURE 2 and are multiplied through secondary emission. Sincethe inputs of channels 12 and 14 are normally maintained at a negativepotential with respect to the output of the channel 10, the electronspassing through the channel 10 cannot enter the channels 12 or 14. Theelectrons reach the end of the channel 10 are eventually \lost to theinner surface of the channel.

When it is desired to gate the electrons through the channel 12 or thechannel 14, a positive voltage pulse is applied to the input of theappropriate channel from the pulse source 22. If the pulse is applied tochannel 12, the electrons emerging from the channel 10 are permitted toenter the channel 12 where they successively strike the surface of thechannel and are further multiplied before they impinge upon the anode16. The path followed by the electrons is shown by the path 50 in FIGURE3. The electrons striking anode 16 are indicated on the oscilloscope 28.The electrons would follow a similar path through the channel 14 if thepulse is applied to that channel. Thus, by applying a positive pulse tothe channel 12 or to the channel 14, gating action results to direct theelectrons at the output of the channel 10 through either the channel 12or the channel 14.

The above gating apparatus would be particularly useful in connectionwith the time-of-flight mass spectrometer such as disclosed in theaforesaid US. Patent No. 2,685,- 035. From the mass spectrometer, ionsof different mass would arrive at the-input of the channel 10 atdilferent time-s. Accordingly, the electrons produced through secondaryemission by the ions of different mass would also arrive at the outputof the channel 10 at correspondingly different times. At the times thatelectrons produced by the ions of a particular mass are expected at theoutput of the channel, the channel 12 may be pulsed to gate'theelectrons through the channel for collection by the anode 16 anddetection by the oscilloscope 28. Similarly, electrons produced by ionsof a different mass would be gated through channel 14 upon theapplication of a pulse to that channel at the proper time.

Although only two channels (12 and 14) have been used in describing thisinvention, it will be recognized that additional channels can beprovided at the output of the channel 10 and the electrons gated throughthe one to which a pulse is applied. If desired, the electrons could begated through more than one channel by applying pulses simultaneously tothe inputs of .two or more channels.

anevgeea Although this invention has been disclosed and illustrated withreference to particular applications, the principles involved aresusceptible of numerous other applications which will be apparent topersons skilled in the art. The invention is therefore to be limitedonly as indicated by the scope of the appended claims.

Having thus described ourinvention, we claim:

1. A gate for a first channel electron multiplier comprising a pluralityof channel electron multipliers positioned relative to the output of thefirst channel to receive electrons emerging from the first channel,

and means. for changing'the potential of at least one of the channels inthe plurality to cause'the electrons emerging from, the first channel toenter only said channel in the plurality.

2. A gate for a firstrchannel electron multiplier comprising a pluralityof channel electron multipliers having their input-s positioned relativeto the output of the first channel to receive electrons emerging fromthe first channel,

means for applyingbiasing'voltages to the inputs of each of theplurality ofchannels to prevent the entrance of electrons emerging fromthe first channel, and means for applyinga-voltage pulse to'at least oneof the inputs of the plurality of channels to cause the electronsemerging from the first channel to enter the pulsed: channel duringapplication of the pulse.

3 A gate for a first channel electron multiplier comprising second andthird channel electron multipliers having their inputs positionedrelative to the output of the first channel to receive electronsemerging from th first channel, 7

means for applying a biasing voltage to the inputs of the second andthird channels to prevent the entrance of electrons emerging from thefirst channel,

and means for applying a voltage pulse to the input of the second orthird channel to cause the electrons emerging from the first channel toenter the pulsed channel during application of the pulse.

4. A gate for a first channel electron multiplier comprising a pluralityof multiplier units positioned relative to the output of the firstchannel to receive electrons emerging from the first channel,

each multiplier unit including a channelelectron multiplier andcollecting means positioned at the output of the channel,

and means for changing the potential of at least one of the multiplierunits in the plurality to cause the electrons emerging from'the firstchannel to enter only the channel in said-onemultiplier unit and toreach the collecting means positioned at its output.

References Gited by i the Examiner UNITED STATES PATENTS 2,826,704 3/58Wiley 313-405 FOREIGN PATENTS 814,134 5/59 Great Brita-in.

DAVID J. GALVIN, Primary Examiner.

2. A GATE FOR A FIRST CHANNEL ELECTRON MULTIPLIER COMPRISING A PLURALITYOF CHANNEL ELECTRON MULTIPLIERS HAVING THEIR INPUTS POSITIONED RELATIVEOT THE OUTPUT OF THE FIRST CHANNEL TO RECEIVE ELECTRONS EMERGING FROMTHE FIRST CHANNEL, MEANS FOR APPLYING BIASING VOLTAGES TO THE INPUTS OFEACH OF THE PLURALITY OF CHANNELS TO PREVENT THE ENTRANCE OF ELECTRONSEMERGING FROM THE FIRST CHANNEL, AND MEANS FOR APPLYING A VOLTAGE PULSETO AT LEAST ONE OF THE INPUTS OF THE PLURALITY OF CHANNELS TO CAUSE THEELECTRONS EMERGING FROM THE FIRST CHANNEL TO ENTER THE PULSED CHANNELDURING APPLICATION OF THE PULSE.